| Title: | Modeling long-term water quality impact of structural BMPs |
| Authors: | Bracmort, K.S., M. Arabi, J.R. Frankenberger, B.A. Engel and J.G. Arnold |
| Year: | 2006 |
| Journal: | Transactions of the ASABE |
| Volume (Issue): | 49(2) |
| Pages: | 367-374 |
| Article ID: | |
| DOI: | 10.13031/2013.20411 |
| URL (non-DOI journals): | |
| Model: | SWAT |
| Broad Application Category: | hydrologic and pollutant |
| Primary Application Category: | pollutant cycling/loss and transport |
| Secondary Application Category: | calibration, sensitivity, and/or uncertainty analysis |
| Watershed Description: | 6.2 km^2 Dreisbach and 7.3 km^2 Smith Fry subwatersheds, which are tributaries of the 50 km^2 Black Creek (and larger Maumee River system) located in Allen County, northeastern Indiana, U.S. |
| Calibration Summary: | monthly (time periods - see comments): Dreisbach: streamflow r2/E = .92/.84 s. runoff r2/E = .91/.80 sus. solids r2/E = .97/.92 mineral P r2/E = .92/.84 total P r2/E =.93/.78 ----------------------------Smith-Fry: streamflow r2/E = .86/.73 s. runoff r2/E = .84/.62 sus. solids r2/E = .94/.86 mineral P r2/E = .90/.78 total P r2/E =.64/.51 |
| Validation Summary: | monthly (time periods - see comments): Dreisbach: streamflow r2/E = .87/.73 s. runoff r2/E = .88/.75 sus. solids r2/E = .86/.75 mineral P r2/E = .86/.74 total P r2/E =.90/.79 ----------------------------Smith-Fry: streamflow r2/E = .81/.63 s. runoff r2/E = .84/.63 sus. solids r2/E = .85/.68 mineral P r2/E = .73/.51 total P r2/E =.73/.37 |
| General Comments: | SWAT was used to evaluate the long-term impact (25 years) if 4 BMPs (field borders, parallet terraces, grassed waterways, and grade stabilization structures) for the two subwatersheds. A senstivity analysis of 30 SWAT input parameters was performed to determine which have the greatest relative impact on streamflow, sediment yield, and total P loss. The values of parameters used to characterize each BMP are given with and without the BMP in place. The impacts of 25-year simulations of no BMPs, BMPs in good condition, and BMPs in varying condition are reported for streamflow, sediment, and total P. Graphical results shown for the complete calibration-validation periods; the complete periods were Jan. 1975 - July 1978, Jan. 1974 - May 1977, Jan. 1975 - July 1978, and Jan. 1975 - April 1977 for Dreisbach streamflow, Dreisbach pollutant losses, Smith Fry streamflow, and Smith Fry pollutant losses, respectively. |
| Abstract: | Structural best management practices (BMPs) that reduce soil erosion and nutrient losses have been recommended and installed on agricultural land for years. A structural BMP is expected to be fully functional only for a limited period after installation, after which degradation of the BMP is likely to lead to a reduction in the water quality improvement provided by the BMP. Assessing the impact of BMPs on water quality is of widespread interest, but no standard methods exist to determine the water quality impact of structural BMPs, particularly as the impact changes through time. The objective of this study was to determine the long-term (~20 year) impact of structural BMPs in two subwatersheds of Black Creek on sediment and phosphorus loads using the Soil and Water Assessment Tool (SWAT) model. The BMPs were represented by modifying SWAT parameters to reflect the impact the practice has on the processes simulated within SWAT, both when practices are fully functional and as their condition deteriorates. The current condition of the BMPs was determined using field evaluation results from a previously developed BMP condition evaluation tool. Based on simulations in the two subwatersheds, BMPs in good condition reduced the average annual sediment yield by 16% to 32% and the average annual phosphorus yield by 10% to 24%. BMPs in their current condition reduced sediment yield by only 7% to 10% and phosphorus yield by 7% to 17%. |
| Language: | English |
| Keywords: | Conservation effects, Phosphorus, Sediment, SWAT, Watershed modeling |